For many years it has been proposed to employ direct fuel injection in spark ignited internal combustion engine, in order to improve engine performance. Spraying fuel directly onto the spark plug provides a rich fuel to initiate combustion, and the combustion chamber provides the air necessary to complete combustion, as compared to the homogeneous mixture of a conventional spark ignited engines where the mixture has to be rich enough in fuel to initiate combustion, but in which there is insufficient air to complete combustion. In this latter case, the combustion must continue in a catalytic converter with the consequent waste of energy.
Previous attempts at direct fuel injection have been inhibited due to the tendency of the sprayed fuel to extinguish the sparking when contacting the spark plug electrodes. As a solution to this problem, it has been proposed to reduce the quantity of fuel directed at the electrodes. Such schemes have avoided direct contact with the spark plug, for example by spraying the fuel in close proximity as illustrated in FIG. 2, by either spraying the fuel in a pattern such that only a portion of the injected fuel contacts the spark plug, or by preatomization of the fuel with air.
Since gasoline is easier to vaporize and ignite than diesel fuel, the gasoline has been preferred as the fuel when injecting fuel for spark ignition.
Since gasoline lacks the lubrication qualities of diesel fuel that are essential to the durability of the injection components, however, the use of diesel fuel would be preferred in such a system, if it is possible to effect ignition of a diesel fuel in an efficient manner, which the ignition system in accordance with the invention accomplishes.
FIG. 1 is circuit diagram of a conventional ignition system employing a reluctor 6 mounted to rotate half engine speed together with distributor rotor 16. In this arrangement, the reluctor generates a pulse in pick-up coil 8 in accordance with distributor and engine rotation. The pulse is shaped and amplified by an ignition module 10, such as a Chrysler ignition module, which in conjunction with battery 34 energizes the ignition transformer 12. Numbers 1 through 5 in the module 10 represent the pin numbers of the Chrysler module 10.
In this system, each spark plug 18, 20, 22, 24, 26, 28, 30. 32 is activated once every two engine revolutions, during the anti-dwell period of the ignition module 10. FIG. 3 illustrates the ignition transformer primary current, in this system, and FIG. 4 illustrates the spark plug current. The position of the distributor rotor 14 determines which spark plug is being activated.
If each cylinder with spark plug has its own ignition system as shown in FIG. 5, the 8 toothed reluctor from an 8 cylinder engine will generate 8 pulses and spark plug firings per engine revolution as shown FIG. 6 instead of the customary spark plug firing every other engine revolution as shown in FIG. 3. The 8 pulses and spark plug firings as shown in FIG. 6 would occur with the reluctor 6 rotating at the same speed as engine, whereas FIG. 4 is shown with the reluctor rotating at the half speed of the engine distributor.
FIG. 7 illustrates the ignition system of FIG. 5 enhanced with auxiliary ignition system as disclosed in my copending patent application Ser. No. 07/637,607, the contents of which are incorporated by reference here. In this arrangement, pick up coil 8 in conjunction with reluctor 6, which rotates at half engine speed for a 4 stroke engine, generates a pulse to activate the ignition module 10 which in turn activates transformer 42 The transformer 42 is a Kettering high voltage inductive discharge transformer with 3 taps for by-pass diodes 46, 48, 50 and 52. These diodes may be 12,000 volt Fagor #HVR-12 diodes. The transformer 42 is tapped to "lock in" the voltage across each diode so that the voltage divides equally between the diodes as described in my patent application Ser. No. 636,607.
The diodes provide a low impedance path for the inductive discharge current from auxiliary transformer 44 which may be a Thordarson CFP-700 transformer with a 230 volt primary and a 10 volt secondary operated with the winding functions reversed so that the 10 volt winding is used as the primary and the 230 volt winding is the secondary. Module 36 is a Chrysler ignition pulse shaper-amplifier module with its current output capacity increased by use of a higher current output transistor. A 1,000 ohm Resistor 38 connects module 36 to the pick coil 8 causing a phase delay allowing module 36 in conjunction with transformer 44 to discharge current after the sparking has been initiated in spark plug 18. Since transformer 44 is of higher volt ampere capacity and lower secondary winding resistance and impedance than the Kettering transformer 42, the current and the sparking at spark plug 18 is greatly increased.
In the arrangement of FIG. 7, a 1.3 ohm "Ballast" resistor 40 and a 0.5 ohm "Ballast" resistor 41 reduce current fluctuation when the starter motor of the engine is engaged, in accordance with a technique well known to those skilled in the art.
FIG. 2 illustrates a known prior art arrangement for a direct fuel injected internal combustion engine. It is noted that in this arrangement the fuel is not sprayed directly onto the spark plug since this would generally extinguish the sparking. Instead, the fuel is sprayed close to the spark plug and depends upon air movement or "swirl" for contact to be made between fuel and sparking. This technique has accordingly been found to be unreliable.